Uranium chelates of di (salicylal) alkylenediimine and process for their preparation



United States Patent-" 2,778,843 URANIUM .CHELATES 0F DI(SALICYLAL)ALKYL- ENEDIIMINE AND PROCESS FOR THEIR PREP- ARATION Horace D. Brown, Plainfield, N. J., and Frederick J. Wolter, Cleveland, Ohio, assignors to the United States of America as represented by the United States Atomic Energy Commission No Drawing. Application April 25, 1949,

a a Serial No. 89,580

25 Claims. (Cl. 260-4291) This invention relates to compounds of uranium and to a process for their preparation, and it especially relates to a process for the separation of'uranium from aqueous solutions. The present invention also relates to the extraction of uranium from organic solvent solutions of the uranium compounds of the subject invention.

Uranium values are present in several types of ores, such as pitchblende, carnotite, and monazite sands. In the case of monazite sands, the amount of uranium values present is low. For example, the U308 content is of the order of 0.4%. The major metal values in monazite sands are rare earth values, primarily as phosphates. Analyses of several samples of monazite sands showed them to contain rare earth oxides (R203) between 40 and 60% and between 19 and 29% P205. In addition, these monazite sands contained thorium values in the amount of 3 to 6.5% ThOz, as well as small amounts of other materials.

By various processes, not forming a part of the present invention, uranium values can be recovered from the uranium-containing ores, including monazite sands. By these recovery processes, there are obtained aqueous solutions of uranium salts. In these solutions other metal salts are present; for example, in solutions obtained by treatment of monazite sand, thorium salts and rare earth metal salts are present. In other recovery processes uranium is obtained from uranium ores as dilute solutions of uranium salts substantially free of other metal salts.

With the development of neutronic reactors for the production of plutonium by neutron bombardment of U it has been found that the neutrons which would normally escape from the reactor can be utilized by placing a blanket of thorium or thorium oxide around the reactor; These neutrons are absorbed by thorium, which is chiefly Th to produce Th The latter decays with a halflife of 23.5 minutes to Pa which in turn decays with a half-life of 27.4 days to U By the use of this thorium blanket desirable Pa and U are produced. By a suitable period of aging most of the Pa will be converted to U However, the maximum amount of U that may be obtained will be about 1% based on the Th content and in the usual case the U content will be less than 0.1%. When the thorium'blanketis used too long before separating the U produced therein, some U will fission and part of the .fis'sion fragments will consist, after aging, of at least some of the rare earth elements. In such a case, it will be necessary in recovering U not only to separate U from thorium, but also it will be necessary to separate U from the radioactive rare earth fission products.

It is an object of the present invention to provide new compounds of uranium. V

A second object of this invention is to provide a process for the preparation of these new compounds of uranium. I

A third object of the present invention is to provide a process for the separation of uranium from an aqueous solution of a uranium salt.

Another object of thisinvention'is to separate uranium from a mixture of uranium and rare earth metals and from a mixture of uranium and rare earth fission products.

A further object of the present invention is to separate uranium from an organic solvent solution of the uranium 'to extract uranium by this invention from aqueous solutions.

Other objects of this-invention will be apparent from the description which follows.

The new compounds of uranium of this invention are i chelate compounds of tetravalent uranium, U(IV), and a di(salicylal)alkylenediimine in which the diimine is represented by the general formula:

. R j R R R wherein R is a member of the group consisting of hydrogen and alkyl radicals and R represents a wide variety of radicals including hydrogen, a halogen, a nitro group, an alkyl group and an aryl group. These diimines are broadly termed di(salicylal)=alkylenediimines wherein the divalent alkylene radical contains at least two carbon atoms and joins the two nitrogen atoms by means of two carbon atoms. The tetravalent uranium chelate compounds are Water-insoluble and are destroyed by aqueous acidic solutions having pH values of less than 2. They are soluble in substantially water-immiscible organic solvents. These chelate compounds may be used, for example, to coat foil which can be used in a neutron-detecting ion chamber, where uranium will fission by neutron-bombardment producing 8- and 'y-radiation that will be detected in the chamber.

Examples of the diimines, from which these chelate compounds are suitably prepared, are as follows: Di(salicylal)ethylenediimine (i. e., di(2-hydroxybenza1)- ethylenediimine) Di 2-hydroxy-3-methoxyb enzal) ethylenediimine Di(Z-hydroxy-S-niethylbnzal)ethylenediimine Di (2, 3 -dihydroxy-6-phenylbenzal) ethylenediimine Di (2-hydroxy-3 -nitrob enzal) ethylenediimine Di (2-hydroxy-3 -bromob enzal) ethylenediimine Di (Z-hydroxy-S -chlorobenzal) ethylenediimine Di (2-hydroxy 3 -chlorobenzal) ethylenediimine Di( 2-hydroxy-3,S-dichlorobenzal) ethylenediimine Di (2-hydroxy-3-chloro-5-tert-butylb enzal) ethylenediimine Di (2-hydroxy-3 -bromo-5 -tert-butylbenzal) ethylenedi'unine Di(2-hydroxy-3-isopropyl-5-chloro-6-methylbenzal)ethylenediimine I Di(2-hydroxy-3,5-dimethylbenzal)ethylenediimine Di (2-hydroxy-3 -chloro-4-tert-butylbenzal) ethylenediimine Di (2-hydroxy-S-tert-butylbenzal) ethylenediimine Di Z-hydroxy-S-chloro-G-m ethylb enzal) ethylenediimine Di(2,3 dihydroxy 5 or 6 tert-butylbenzal) ethylenedi- Di 2-hydroxy-5-tert-ar'nylbenzal) ethylenediimine Di(2-hydroxy-3-methyl-5-tert butylbenzal)ethylenediimine Di(diamylsalicylal)ethylenediimine 2 Di(Z-hydroxy-(6-methyl-5-tert-butyl-and or-4-m'ethyl-5- tert-butyl) -benzal) ethylenediimine 3 Di (2-hydroxy-4,6-dimethylbenzal) ethylenediimine Di(salicylal)propylene-1,2-diimine I H C=NOH- O rn-N=o Footnotes in following column.

Patented Jan. 22, 1957 -on no- Di(salicy1al) butylene-2,3 -diimine [on no.

We have also found that these tetravalent uranium chelate compounds can be made by contacting an aqueous solution containing a tetravalent uranium salt, such as UC14. and U(N0a),4, andhavinga pH between 2 and 7 with the di(salicylal)alkylenediimine. The diimine and uranium react to form a water-insoluble compound. Two molecules of the diimine react with uranium by replacing hydrogen atoms of the 2-hydroxyl groups. Also, tetravalent uranium h aving a coordination number of eight form'sa coordinate bond with the two nitrogen atoms of each molecule of the diimine, wherein uranium shares elec trons of the-nitrogen atoms. The chelate compound precipitatesfrom the aqueous solution. It is separated by filtration or other suitable means. The diimine may be usedas an organic solvent solution and then the chelate compound isprepared bycontactingthe aqueous solution with. this organic solvent solution andv separating an aqueous phase and an organic solvent phase containing.

the-.chelatecompound. For some solvents a true solution. is. not formed; instead, the solvent removes the chel'ate compound by a preferential wetting action. Of cour se,-the.diimine maybe used alone in the initial. contacting withtheaqueous solution. and. the organic solvent added before removal of chelate compound. The-organic solventphase may be treatedfurther to recover. the chelate compoundbyremoving the organic solvent, for example, y. Y l liZ%F Q :i-..

In another embodiment of this invention,,urahium 'is separated r.9;. hea i9u solu on wnta nai s e valent salt and having a pll betw en 2 and 7'bycontacting with, an ;,o a solvent solu o separating an aq usphase an an'organic solvent extract phase co In the for fli sthe fi wi latawmpa n 1 uranium chelateco rnpioundit is pr ried to use less than the stoichiometric. mount. of-the diimine, sothat resultant mea t ant ater ee fiu d. i n However, inth seconde rnbodiment, wherein the process isfort e s paration of uranium, it is preferred that greater than a toichiometric amount of .diimine is us edfso that the maximurnamountof uranium is chelated extr'acted fromthe aqueoussolution. f,

The pH of betweenl and], preferably between 2 and 6, tor the aqueous solution'of fa tetravalent uranium salt is in taine d,.jby pan acet'ate bufier in a,suitable concentration. 'An acetate butfe'r'compri'ses' acetic 'acid,;analkali acetate, such assod ium acetate and ammonium 'acetate,

and mixtures of acetic acid and alkali acetate. The K The position of the t ertbutylgrouphasr'not beenfestablished. An o-hydroxyhenzaldehyde 'was..-prep,ared from- 2-hydroxy-4-tert-butylphenol according cto th .Duft method-. .(J. Chem. Soc. 1941, 547 -50) by reacting said phenol andhxw methylenetetra nme -in the presence. of anhydrous glycerol and glyceroborrc acid at 1 00 C.-, cooling to 11 0"v C., adding dilute sulfuric acid, recovering an o-hydroxy'benzaldehyde derivative by steam d1St1 ll2lt10Il of the acidified reaction mixture, and condensing said salicyhldehyde derivative with ethylenediamine in a molal-ratio of 2.t0 1.

The parent ohydroxyaldehyde was prepared by the Butt reaction, supra, from com-mercially available diamylphenol.

The parent o-hydroxyaldehyde wasprepared by the Duff reaction, supra, from 3-methy1-4tert-butylphenol. Two isomers are possible, but noattempt wasmade to identify the aldehyde. V

tionsof sodiumacetate and aceticacid for various pH values are given. Th concentrations o f-ammdnium ace= tate or mixtures of ammonium acetate and" acetic acid that will provide certain pH values are as follows:

of the- 'diimine, and

recess for the prepar'ation of the r Concentra- Concentra- For pH of tlon of tl on ot Ammonium .Acetic Acetate, M Acid, M

It the aqueous solution before the addition of acetate buffer containsfr'ee inorganic acid, such as nitric acid and hydrochloric acid, so that the solution hasa pH less than 2, the excess acid cah'beelirninated' by adding alkali acetatein an amount sufiicient to neutralize inorganic acid as well as toprovidethe required amount of alkali acetate bufier. If the reactionjbetween inorganic acid and alkaliacetate doesnotjprovide the requisite amount of acetic acid for the desired pH value, acetic acid is added. Of course, when the initial aqueous solution has a very great concentration of inorganic acid, part of the acid may be neutralized by the use of a strong base, such as sodium'hydroxide'. I

The organic solvent for the present invention is a sub stantially water-immiscible organic compound which is liqnid at the temperature of carrying out the separation and preparation processes. Examples of suitable types of organic solventsare: halogenated hydrocarbonsyhydrocarbons; alcohols; ethers; esters; ketones; and nitroparaiiins. vSpecific examples are: chloroform; carbon tetrachloride; trichloroethylene; chlorobenzene; hexatluoroxylene; petroleumether (having a boiling range between 35 and 55 C.); benzeneftolu'e ne; xylene, such as p-xylene; benzyl alcohol; cyclohexanol; diisopropyl ether; diethylfeth'er; n-butyl acetate; methyl isobutyl kctone; cycloh'e'xanone;andhitrbththe.

The efli'ciencypf i'chelation extraction is not identical for all the di(salicylal)alkylenediirnines. The'arnount of, or the concentration inthe organic solvent of, the chelating agent, i. a, the di(sali-cylallalkylenediimine, may be varied widely. For any'particular operation the concentration will vary with the concentration of 'tetravalent uranium salt'in-the aqueous solution. The ratioof'organic solvent solution to aqueous solution may be varied widely, and thepreferredrange is between 5 to 1 and l to 5. The temperature at which the' process is carried but may be varied considerably, for example, between room temperature'and95 C. ,7 V In thepreparation andextraction processes the time'of contact between "th'e' a'quequssolution and the- 'diir'n'ine varieswith thetemperature, the uranium concentration, and the degree of fchelati'on-ext'raction' desired. Using tracer-solutions, such as 10*?" UGV) salt, a periodof one to jeight minutes 'at room temperature is'adequate; however, with-higher concentrations of uranium, a contact time of at least one-half hourfis preferred;

In another aspect of the second 'embodim'e'nt 'of the process of this invention, the-aqueous solution also contains natural-occurring rare earth metal; salts "or salts of rare earth fission products. Inthis cas'e, uranium is chelated-ext'r'act'ed'and the trivalent'rare earth 'valt'l'es'remain in the aqueous solution. Thus, a mixture ofur'a'n-ium and trivalent rare earth valuesmay-be-separated'by' forming an" aqueous solution thereof with uranium the tetravalentstate, using a suitable iediicingag'cn't if the dissolutionproduc'ed a uranyl 'salhprovidin' e requisite pH" by means of the acetate butter, am ne-n 'chlating-itra-eting as d'e'scrib'ed above.

2 and separating an organic solvent phase and aqueous extract phase containing a uranium salt.

A further embodiment comprises a combination of the second and third embodiments, whereby uranium is transferred from one aqueous solution to another aqueous solution through the intermediate chelation-extraction. This combination is useful, for example, when sodium uranyl acetate, NaUO2(OAc)3, has been dissolved and it is desirable to have a uranium solution free of sodium cations. Uranium is reduced to the tetravalent state and the combination process is carried out. The final aqueous solution of uranium salt contains no sodium cations.

Other embodiments will be apparent to those skilled in the art.

The following examples taken either alone or in con1- bination are illustrative of the foregoing embodiments of the invention, both compounds and process. Di(2,3-dlhydroxy-S or 6-tert-butylbenzaDdiethylenediamine is re fererd to in the examples as Disal. The experiments were carried out at room temperature.

EXAMPLE I An ethyl alcohol solution of di(saIicyIaDethylenediimine, i. e., di(2-hydroxybenzal)ethylenediimine, and uranous acetate, U(OOCCH3)4, was refluxed and a small amount of UC14; an aqueous solution containing a tetravalent thorium salt; and an aqueous solutioncontaining a tetravalent zirconium salt. chloroform solutions of Disal. After separation of the aqueous and chloroform phases, they were analyzed for the distribution of the metal values. Uranium and thorium were determined by alpha-counting and zirconium was determined by means of p-dimethylaminoazophenylarsonic acid. The percentage of the cation extracted for each experiment is presented below in Table II.

Table 11 pH of Aque- Percent Metal Cation ous Solution Values Extracted EXAMPLE IV The behavior of Disal with various cations was determined by extraction experiments using tracer amounts and milligram amounts of ions from acetate-buffered solutions, 0.1 to 1 M in total acetate, and using chloroform as the organic solvent. The experiments were carried out in separatory funnels or in a microextraction apparatus in which agitation of phases was produced by a gas stream. In all cases, the volume of chloroform was equal to that of the aqueous solution. Tracer solutions contain concentrations of the order of 10* M.

Radioactive 33-year Cs was used to determine the distribution of cesium in Disal extractions. Activities were measured by checking the radioactivity of CsClO4 precipitates from the aqueous and organic solvent phases with a Geiger-Muller counter, which was the copper wall type with a mica window 5.2 mg./cm. in thickness.

The behavior of barium was determined over a wide pH range wtih 12.8-day Ba The tracer was recovered from the aqueous and organic solvent phases as BaCOa and the activity was determined with an electroscope of 'the Lauritsen quartz fiber type with a 2.4 mg./cm. aluminum window. 1 a

A solution of UXI activity (24-day Th was prepared by the ether extraction of uranyl nitrate. The buffered aqueous solution was extracted with Disal solution in chloroform, and the tracer was recovered by La(OH)3 precipitations.

For extractions of zirconium, a sample of carrier-free E D0 zirconium tracer was used. Absorption measurements Table I showed that the activity was at least 90% pure 68-day Zr The tracer was recovered by Fe(OH)3 precipitations Percent and the activity determined with an electroscope. The behavior of Disalf solution in chloroform with Element 0 1 E 1 l tracer amounts of the various cations is summarized in 1st xper manta I Table III.

Table III 30.9 33.8. 49.9 48.4.

2-:- I. A r rear 8:3 6:9 (by difference). n s i t i ifi Exizrszzte d EXAMPLE II 5+ 123 31,; A uranium tetrahydroxide precipitate was contacted 6 32 with a chloroform solution of di(salicylaDethylenediimine. 9 The hydroxide was slowly attacked and the chloroform 21% if? layer gradually acquired the red color of the tetravalent Mixture of na and Y+|+ g: 8.3? uranium complex or chelate compound. 2150 1216 EXAMPLE III 312% 353 The following aqueous solutions each containing an $38 1 k acetate butfer were prepared: an aqueous solution con? taining a uranyl salt; an aqueous solution containing a 5.25 85.4 few milligrams of a tetravalent uranium salt, namely,

These solutions were contacted with.

of each experiment were separated. The distribution of rare earth elements was determined by their radioactivities using an electroscope. The data are summarized below in Table IV.

Table IV Percent Rare Earth Elements Extracted pH of Aqueous Solution The data in Examples 111, IV, and V illustrate that uranium is separated from trivalent rare earth elements with a high degree of efliciency. The data also show thorium will be chelated-extracted by the process of the present invention. After the extraction of thorium and tetravalent uranium values from the organic solvent solution of their chelate compounds by using an aqueous solution having a pH of less than 2, the uranium and thorium can be separated by other processes not forming a part of the present invention.

The examples, presented above, of this invention were batch experiments, but the chelation-extraction step and ire-extraction step may be effected by the use of batch, continuous batch, batch countercurrent, or continuous countereurrent methods. It is preferred to use batch methods for the chelation-extraction step because of the timerequired for maximum chelation.

The foregoing illustrations and embodiments of this invention arenot intended to limit its scope, which is to be limited entirely by the appended claims.

What is claimed is:

1. A tetravalent uranium chelate compound of a di- (salicy-lal)alkylenediimine wherein the divalent alkyl'ene radical contains at least two carbon atoms and joins the two nitrogen atoms by means of two carbon atoms.

2. A tetravalent u-raniumchelate compound of, a di- (salicylal)ethylenediimine.

3. A tetravalenturanium chelate compound of di(2,3- dih-ydroxy-tert-butylbenzal)ethylenediimine wherein the imine was prepared from 2-hydroXy-4-tert-butylphenol by reacting said phenol and hexamethylenetetramine in the presence of anhydrous glycerol and glyceroboric acid at 150 C cooling to 110 C., adding dilute sulfuric acid,

recovering an o-l ryd;rcx-y-benzalclehydev derivative by steam distillation of the acidified reaction mixture, and condensing said salicylaldehyde derivative with ethylenediaminc in a molal ratio of 2 to 1.

4. A tetravalent uranium chelate compound of di(2- hydroxy-3-chloro-5-tert-butylbenzal) ethylenediimine.

5'. A tetravalent uranium chelate compound of di(2- hydroxybenzal)ethylenediimine.

6. A process for'the preparation of a tetravalent uranium chelate'compound of a di(s'alicylal)alkylenediimine wherein the divalent alkylene radical contains at least two carbon atoms and joins the two nitrogen atoms by means of two carbon atoms, which comprises contacting an aqueous solution containing a tetravalent uranium salt and maintained at a pH between 2 and 7 by an acetate buffer with said di(salicylal) alkylenediimine, and separatingthe resultant tetravalent uranium chelate compound.

7*. The process of claim 6 in which the di(salicylal)- alkylenediimine is a di(salicylal)ethylenediimine.

8i A process for the preparation of a tetravalent uranium cheiate compound of a di(salicylal)alkylenediimine til) wherein the divalent alkylenc radical contains at least two carbon atoms-and joins the two nitrogen atoms by means of two carbon atoms, which comprises contacting an aqueous solution containing a tetravalent uranium salt and maintained at a pH between 2 and 7 by an acetate buffer with a solution in a substantially water-immiscible organic solvent of said di(salicylal)alkylenediimine, and separating an aqueous phase and an organic solvent extract phase containing the tetravalent uranium chelate compound.

9. A process for the separation of uranium from an aqueous solution containing a salt of tetravalent uranium and containing an acetate buffer to provide a pH between 2 and 7, which comprises contacting said aqueous solution with a solution in a substantially water-immiscible organic solvent of a di(salicylal)ethylenediimine,and separating an aqueous phase and an organic solvent extract phase containing the resultant tetravalent uranium chelate compound.

10. The process of claim 9 in which the di(salicylal)- ethylenediimine is 'di(2,3 dihydroxy-tert-butylbenzal) ethylenediimine wherein the imine was prepared from 2- hydroxy-4-tert-butylphenol by reacting said phenol and hexamethylenetetramine in the presence of anhydrous glycerol and glyceroboric acid at 150 (3., cooling to 0., adding dilute sulfuric acid, recovering an ohydroxybenzaldehyde derivative by steam distillation of the acidified reaction mixture, and condensing said salicylaldehyde' derivative with ethylenediamine in a molal rado of 2 to l.

11. The process of claim 10 in which the organic solvent is chloroform and the pH of the aqueous solution is between 2 and 6.

12. The process of claim 9 in which the organic solvent is a xylene, the pH of the aqueous solution is between 2 and 6, and the di(salicylal)ethylenediimine is di(2,3-dihydroxydert-butylbenzal)ethylenediimine wherein the imine was prepared from 2-hydroxy-4-tert-butylphenol by reacting said phenol and hexamethylenetetramine in the presence of anhydrous glycerol and glyceroboric acid at C., cooling to 110 0, adding sulfuric acid, recovering an o-hydroxybenzaldehyde derivative by steam distillation of the acidified reaction mixture, and condensing said salicylaldehyde derivative with ethylenediamine in a molal ratio of 2 to 1.

13. The process of claim 9 in which the organic solvent is methyl isobutyl ketone, the pH of the aqueous solution is between 2 and 6, and the di(salicylal)ethylenediimine is di(2,3-dihydroxy-tert-butylbenzal)ethylenediimine wherein the imine was prepared from 2-hydroxy-4- tert-butylphenol by reacting said phenol and hexamethylenetetramine in the presence of anhydrous glycerol and glyceroboric acid at 150 C., cooling to 110 C., adding dilute sulfuric acid, recovering an o-hydroxybenzaldehyde derivative by steam distillation of the acidified reaction mixture, and condensing said salicylaldehyde derivative with ethylenediarnine in a molal ratio of 2 to l.

14. The process of claim 9 in which the organic solvent is chloroform, the pH of the aqueous solution is between 2 and 6, and the di(sa1icylal)ethylenediiniine is di(2-hydroxy-3-chloro-S-tert-butylbenzal) ethylenediimine.

'15. The process of claim 9 in which the organic solvent is chloroform, the pH of the aqueous solutionis between 2 and 6, and the di(sal-icyial)ethylenediimine is di (Z-hydroxybenzal) ethylenediimine.

16. A process for the separation of uranium from an aqueous solution containing a salt of tetravalent uranium and an acetate butter to provide a pH between 2 and 7, which comprises contacting said aqueous solution with a solution in a substantially water-immiscible organic solvent of a di(salicylal)alliylenediimine wherein the divalent alkylene radical contains at least two carbon atoms ahd'join's; the twonitrogen atoms by means of two carbon atoms, separating an "aqueous phase and an organic solvent extract'phase containing the resultantftetravalent swam , 9 uranium chelate compound, contacting said organic solvent extract phase with an aqueous acidic solution having a pH of less than 2, and separating an organic solvent phase and an aqueous extract phase containing a uranium salt.

17. A process for the separation of uranium from a mixture of uranium and rare earth elements, which comprises dissolving said mixture in an acid solution, providing an acetate buffer in an amount sufiicient to provide a pH of the aqueous solution between 2 and 7, contacting the resultant aqueous solution containing a tetravalent uranium salt and trivalent rare earth salts with a solution in a substantiallywater-immiscible organic solvent of a di(salicylal)alkylenediimine wherein the divalent alkylene radical contains at least two carbon atoms and joins the two nitrogen atoms by means of two carbon atoms, and separating an aqueous phase containing salts of said rare earth elements and an organic solvent extract phase containing the resultant tetravalent uranium chelate compound.

18. A process for the separation of uranium from a substantially water-immiscible organic solvent solution of a tetravalent uranium chelate compound of di(salicylal)- alkylenediimine wherein the divalent alkylene radical contains at least two carbon atoms and joins the two nitrogen atoms by means of two carbon atoms, which comprises contacting said organic solvent solution with an acidic aqueous solution having a pH less than 2, and separating an organic solvent phase and an aqueous extract phase containing a uranium compound.

19. The process of claim 18 in which the tetravalent uranium chelate compound is a chelate compound of di- (2,3-dihydroxy-tert-butylbenzal)ethylenediimine wherein the imine was prepared from 2-hydroxy-4-tert-butylphenol by reacting said phenol and hexamethylenetetramine in the presence of anhydrous glycerol and glyceroboric acid at 150 C., cooling to 110 0., adding dilute sulfuric acid, recovering an o-hydroxybenzaldehyde derivative by steam distillation of the acidified reaction mixture, and condensing said salicylaldehyde derivative with ethylenediamine in a molal ratio of 2 to 1.

20. The process of claim 18 in which the tetravalent uranium chelate compound is a chelate compound of di (2-hydroxy-3 -chloro-5-tert-butylbenzal) ethylenediimine.

21. The process of claim 18 in which the tetravalent uranium chelate compound is a chelate compound of di(Z-hydroxybenzal) ethylenediimine.

22. A process for the separation of uranium and thorium from a mixture of uranium, thorium, and rare earth elements, which comprises dissolving said mixture in an acid solution, providing an acetate butter in an amount I 10 suflicient to provide a pH of the aqueous solution between 2 and 7, contacting the resultant aqueous solution containing the tetravalent uranium salt, a thorium salt, and trivalent rare earth salts with a solution in a substantially water-immiscible organic solvent of a di(salicylal)alkylenediimine wherein the divalent alkylene radi cal contains at least two carbon atoms and joins the two nitrogen atoms by means of two carbon atoms, and separating an aqueous phase containing salts of said rare earth elements and an organic solvent extract phase containing the resultant tetravalent uranium chelate compound and thorium chelate compound.

23. The process of claim 22 in which the organic solvent is chloroform and the di(salicylal) alkylenediimine is di(2,3-dihydroxy-tert-butylbenzal)ethylenediirnine prepared from 2-hydroxy-4-tert-butylphenol by reacting said phenol and hexamethylenetetramine in the presence of anhydrous glycerol and glyceroboric acid at 150 C., cooling to (3., adding dilute sulfuric acid, recovering an o-hydroxybenzaldehyde derivative by steam dis tillation of the acidified reaction mixture, and condensing said salicylaldehyde derivative with ethylenediamine in a molal ratio of 2 to l.

24. A process for the separation of thorium from a mixture of thorium and rare earth elements, which comprises dissolving said mixture in an acid solution, providing an acetate buffer in an amount sufiicient to provide a pH of the aqueous solution between 2 and 7, contacting the resultant aqueous solution containing a thorium salt and trivalent rare earth salts with a solution in a substantially water-immiscible organic solvent of a di(salicylal) alkylenediimine wherein the divalent alkylene radical contains at least two carbon atoms and joins the two nitrogen atoms by means of two carbon atoms, and separating an aqueous phase containing salts of said rare earth and an organic solvent extract phase containing the resultant thorium chelate compound.

25. The process of claim 24 in which the organic solvent' is chloroform and the di(salicylal)alkylenediimine is di(2,3-dihydroxy-tert-butylbenzal)ethylenediimine prepared from 2-hy-droxy-4-tert-butylphenol by reacting said phenol and hexamethylenetetramine in the presence of anhydrous glycerol and glyceroboric acid at 0., cooling to 110 C., adding dilute sulfuric acid, recovering an o-hydroxybenzaldehyde derivative by steam distillation of the acidified reaction mixture, and condensing said salicylaldehyde derivative with ethylenediamine in a molal ratio of 2 to 1.

No references cited. 

1. A TETRAVALENT URANIUM CHELATE COMPOUND OF A DI(SALICYLAL) ALKYLENEDIMINE WHEREIN THE DIVALENT ALKYLENE RADICAL CONTAINS AT LEAST TWO CARBON ATOMS AND JOINS THE TWO NITROGEN ATOMS BY MEANS OF TWO CARBON ATOMS. 